Secondary zoonotic dog-to-human transmission of SARS-CoV-2 suggested by timeline but refuted by viral genome sequencing

Purpose The risk of secondary zoonotic transmission of SARS-CoV-2 from pet animals remains unclear. Here, we report on a 44 year old Caucasian male presenting to our clinic with COVID-19 pneumonia, who reported that his dog displayed respiratory signs shortly prior to his infection. The dog tested real-time-PCR (RT-PCR) positive for SARS-CoV-2 RNA and the timeline of events suggested a transmission from the dog to the patient. Methods RT-PCR and serological assays were used to confirm SARS-CoV-2 infection in the nasopharyngeal tract in the dog and the patient. We performed SARS-CoV-2-targeted amplicon-based next generation sequencing of respiratory samples from the dog and patient for sequence comparisons. Results SARS-CoV-2 infection of the dog was confirmed by three independent PCR-positive pharyngeal swabs and subsequent seroconversion. Sequence analysis identified two separate SARS-CoV-2 lineages in the canine and the patient's respiratory samples. The timeline strongly suggested dog-to-human transmission, yet due to the genetic distance of the canine and the patient's samples paired-transmission was highly unlikely. Conclusion The results of this case support current knowledge about the low risk of secondary zoonotic dog-to-human transmissions of SARS-CoV-2 and emphasizes the strength of genomic sequencing in deciphering viral transmission chains.

Automated summary

This study reports a case of a COVID-19 patient who discovered that his dog exhibited respiratory symptoms shortly before his own infection. The dog tested positive for SARS-CoV-2 and genomic sequencing revealed two separate lineages of the virus in both the dog and the patient's samples. The timeline suggests dog-to-human transmission, although direct transmission is highly unlikely due to the genetic distance between the dog and the patient.